In recent years many previously clean water sources have been found to be contaminated with dispersed oils which are often present as oil-in-water emulsions. A further source of contamination arises from presence in the water of pernicious slightly soluble organic compounds such as benzene, toluene, xylene, halogenated hydrocarbons, ethoxylated glycols, etc. These noxious contaminants are among the more difficult compounds to remove from water, and indeed most are carcinogenic. In the present inventor's U.S. Pat. No. 6,180,010 it is disclosed that the compositions described in the inventor's U.S. Pat. Nos. 5,437,793; 5,698,139; and 5,837,146, and 5,961,823 (all of which disclosures are hereby incorporated by reference) have extremely strong affinities for the aforementioned contaminants in water; and that when aqueous streams containing these noxious contaminants are passed through filtration media incorporating these compositions, the contaminants are immobilized at the media, as a result of which concentration levels of the contaminants in the filtrate may be reduced to very low values.
Filter configurations incorporating the said compositions may be based on various water permeable substrates, such as shredded, spun or otherwise configured polypropylene or shredded or spun cellulose, which substrates are infused or otherwise treated with the absorbent compositions, which are then cured. These substrates may be packed or otherwise disposed in a cartridge or canister filter; or can be formed into cured and infused bag filters which can be emplaced in canisters through which the contaminated water is flowed. Similarly the said compositions can be incorporated into or upon other filtering substrates and media, such as paper, including compressed pulp materials, particulate porous foamed plastics, mineral particulates such as perlite and vermiculite, and particulate, fibrous or porous ceramic or porous (e.g. sintered) metal substrates and media.
In a first copending provisional patent application of the present inventor, a further filtration medium and method for its preparation is disclosed which while incorporating certain components of the absorbent compositions of my prior patents, has unexpectedly been found to have markedly superior properties when used as such an absorbent composition in the filtration of organic contaminants from aqueous systems, as for example in removing oils from an oil-in-water emulsion. These further compositions are prepared in part from the absorbent compositions of my prior art patents, which as disclosed in the patents are the reaction product of an oil component and a methacrylate or acrylate polymer component. The absorbent compositions disclosed in the aforementioned copending provisional application are prepared by further combining such prior art reaction product (herein called “reaction product A”) with a photoinitiator system before infusing the combination into the fluid-pervious filtration media. Subsequent exposure of the infused filtration media to actinic UV radiation, effects a very rapid in situ curing of the infused composition, and results in a filter having markedly improved filtration characteristics. Although applicant is not bound by any specific theory, it is hypothesized that the UV in situ curing may result in extensive additional cross-linking of the infused absorbent, with consequent hardening of the infused composition, and pore sizes in the filtration media may in consequence be much smaller than in the filters of my prior methodology. Regardless of the precise mechanism involved, filters so prepared exhibit higher back pressure in use, with consequent increased dwell time for the aqueous streams being passed through the filter. The filters are among other things found to be much more efficient in breaking oil-in-water emulsions than filters prepared by the inventor's prior methodology and compositions. For this reason, and for convenience, such filters shall be referred to herein as “EB” filters, and the corresponding infusion compositions shall at times be referred to as “EB” absorbent compositions. In contrast the filters prepared by the inventor's prior patented methodology and compositions shall, again for purposes of convenience, be referred to as “PA” filters and “PA” absorbent compositions.
In the general method for preparing an EB filter in accordance with the disclosure of said first copending provisional application, a homogeneous thermal “reaction product A” is initially prepared from an oil component and a polymer component, as in my earlier cited patents. The thermal reaction product A here is preferably prepared in a temperature range of 350° to 550° F., and more preferably at a range of from about 400 to 500 deg. F. A photoinitiator system is separately prepared from a monomer cross-linking agent, a catalyst, and a wetting agent, i.e. an oligomer/adhesion promoter/cross-linking agent. An infusing solution is then prepared by combining the reaction product A and the photoinitiator system together with a solvent such as acetone. This solution is infused into the filtration media, e.g. a conventional filtration cartridge containing a filtration substrate such as fibrous polypropylene. The infused cartridge or other infused substrate is then exposed to UV radiation for a short period, usually of the order of several minutes to effect the desired curing. The EB filter is then ready for use.
In a second copending provisional patent application of the present inventor, it is additionally disclosed that in many applications the absorbent compositions of my aforementioned patents are improved by a drastic increase in the ratio of oil component to polymer component. Typically for example the oil component may be increased to above 95% and preferably to around 98% by weight of the two components. These higher oil blends appear to have higher affinity for the more soluble organic compounds such as benzene and low molecular weight chlorinated solvents. Also here the thermal reaction product of oil and polymer component is preferably prepared at a temperature range of 350 to 550 F., and more preferably at a range of from about 400 to 500 deg. F. The filtration media that result after infusion, as well as the infusing compositions, shall be referred to herein by the designation “HO”, which is suggestive of the high content of the oil component
The term “absorbent composition” will be used herein as one of convenience for identifying the said compositions of my aforementioned patents, and will be used as well in referring to the additional compositions disclosed in my cited first and second copending provisional patent applications. The specific mechanism by which the noxious contaminants are removed from aqueous streams by conjunctive use of such “absorbent compositions” is not completely understood, and could include attachment and/or fixation of such contaminants by mechanisms which technically involve various physical and/or chemical interactions. The term “absorbent” as used herein is intended to encompass all of these possible mechanisms.